Real-Time Detection of Micro-RNA Using Cantilever-Based Biosensors

MicroRNAs (miRNAs) are short non-coding segments of RNA (~ 22 base pairs) recently found to be post-transcriptional regulators of gene expression in higher organisms.  Since their discovery, many miRNAs have been identified as important biomarkers of various disease states, such as cancer.  Furthermore, they represent a new class of circulating nucleic acids (CNAs) (i.e. those present in flowing bodily fluids).  Thus, the ability to measure miRNA in complex liquid matrix at sensitive levels presents an important diagnostic opportunity.  We demonstrate the high potential of dynamic-mode piezoelectric cantilever biosensors for making real-time measurements of miRNA (hsa-let-7a) in complex liquid matrix over a large dynamic-range.  Binding response is measured by added-mass effect on resonant frequency caused by hybridization between miRNA and immobilized DNA probes.  Binding was examined in a variety of liquid formats including pure buffer, serum, and liquid matrix containing a high background of non-target miRNA.  Based on concentration-dependent sensor response, limit of detection is competitive with existing technology at sub-picomolar levels.